Thevenin technique solving problem -- getting wrong answer

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The forum discussion centers on the application of the Thevenin technique to determine the voltage across a capacitor (Vc) after closing a switch. The user initially calculates the Thevenin voltage (Vth) as 0.7V using the formula Vth = 21/(60+30) * 30. However, the correct final voltage across the capacitor is 7V, as clarified by the user’s realization that the correct calculation is 30 * (21/(60+30)) = 7V. This highlights the importance of correctly applying the Thevenin theorem in circuit analysis.

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sciman
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Hi

Can you tell me please what I am doing wrong here
upload_2015-4-15_16-15-57.png

I need to find the Vc function after we close the switch.
To do this, I calculate the Thevenin equivalent circuit.
I calculate Vth to be 21/(60+30) times 30, which makes 0.7V but why the answer is 7V?
Basically the answer is Vc=7x(... which means that final voltage of capacitor is 7V and not 0.7V.
Any idea?

thanks
 
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Ehm hm, 30x(21/(60+30))=7
 
I am embarassed
 
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